Cathode for electron discharge devices



Au -2e, 1947.

w, WIDMAIER 2,426,255

CATHODE FOR ELECTRON DISCHARGE DEVICES Filed Aug. 30, 1945 ATTO R N EYPatented Aug. 26 1947 CATHODE FOR ELECTRON DISCHARGE DEVICES WilliamWidmaier, Elizabeth, N. J., assignor to Federal Telephone and RadioCorporation, New York, N. Y., a corporation of Delaware ApplicationAugust 30, 1945, Serial No. 613,455

18 Claims.

This invention relates to electrodes for electron discharge devices andmore particularly to the wire mesh or metal strip type of cathodestructures as employed in gas or vapor types of rectifier tubes of highcurrent carrying capacities.

The improved emitter structure of the invention is designed to produce ahigh degree of electron emission with a minimum expenditure of heatingenergy and to provide a cathode structure of large electron emissionsurface areas with relatively reduced heat radiation. Because of itsregenerative properties, the filament operates at substantially auniform temperature over its entire length-to a much greater degree thanother similarly shielded filamentary type cathodes. It is of a formationand assembly offering structural or mechanical strength such as to berigidly self-supporting and to resist deformation under the infiuence ofheating in its operation such as might impair the proper emissioncharacteristics. It is further designed to be particularly compactoffering advantages in its structural embodiment and with the furtheradvantage of permitting its being made of very thin metal to have highresistance values while maintaining the required mechanical strength forefficient operation over long periods of use.

In addition to its desirable self-supporting rigidity, the improvedemitter is of a structural design which maintains the general shape andrelative position of the electron emission surfaces substantiallyconstant irrespective of the expansion and contraction under temperaturechange so as to maintain its electrical characteristics constant undervariable operating conditions.

The aforesaid structural and operational advantages are successfullyattained by an improved emitter electrode or cathode structure composedof strips of metal which are folded along transverse lines alternatelywith reverse folds. The resulting strips of accordion pleated form areinterfolded with the strips positioned in relative angular relation withinterweaving to effect alternate positioning of the panels or planesections.

The developed structure produces a fabric strip type of electrodecomposed of two strips in interlocked and intersupporting relation ofsuch character as to materially strengthen the resulting structureagainst lateral forces such as magnetic pull and likewise to resistdeflection or sagging under heated condition of use. The structuralreinforcement by the interfolding of the strips accordingly obtains thebenefits of the mechanical strength of the metal fabric on edge in twodirections thereby avoiding the weakness of single strip corrugated orpleated formations of metal strip electrodes as heretofore proposed. Aswill be appreciated the strengthening effect as thus contributed permitsof employing wire fabric strips of extremely fine gauge wire and fabricthickness with proportionate reduction of current consumption.

The described and other features and advantages of the presentimprovements will be more fully understood by reference to theaccompanying drawing wherein like reference characters are applied tothe corresponding parts in the several views.

In the drawings:

Fig. 1 is a perspective view of a portion of the improved electrodestructure composed of metal strip interfolded or interwoven in angularrelation;

Fig. 2 is a perspective view showing the folded strips separated and intheir angular relation for interfolding;

Fig. 3 is a View partially in central vertical section and partially inelevation illustrating an embodiment of the invention in a gas filleddiode type rectifier tube and Fig. 4 is a detailed vertical sectionalview illustrating the mounting of the electrode in end elevation.

Referring to the drawings wherein there is disclosed one embodiment ofthe invention as illustrative of the principle employed in theproduction of the improved type of metal strip electrode, the emi ter isshown employed as the cathode of a gas filled diode-type rectifier tubewhich may be of the mercury vapor type. The improved cathode structurein accordance with the invention is preferably made from strips l and 2of metal fabric which may be of fine gauge nickel wire coated withthermionically active material such as barium, calcium and/or strontiumoxides. The metallic strips, of elongated ribbon form and of uniformwidth, are in their preparation initially folded as indicated in Fig. 2upon equally spaced transverse lines. The spacing correspondssubstantially to the width of the ribbon or strip and these folds 3 aremade or turned successively in opposite directions to produce aresulting folded ribbon of zig-zag or accordion pleated progression. Twoof the strips thus folded are relatively positioned with their foldededges in angular relation as illustrated in Fig. 2 showing therespective strips in their angularly displaced relation for interfoldingto complete the cathode structure.

With the strips l and 2 thus angularly disposed they are interfolded asshown in Fig. 2 by interweaving wherein the folds or bends of each stripembrace or enfold a free edge 5 of the formed rectangular panels 5 ofthe associated companion strip. In this mutual interfolding of thestrips as shown the folds or bends of a given strip embrace free edgesof the panels of the other strip alternately at opposite sides so that arigid type of interlocking is effected and wherein as will be noted themetal on edge relation of the respective strips is angularly disposed in90 angularity upon compression of the folded structure. In consequencethere is metal fabric on edge strength effective in angularly disposedtransverse directions thereby adding considerable strength to theassembled structure.

In the completed assembly of the emitter structure as shown in Fig. 1the rectangular panels formed by the folding assume an acute angularrelation with relation to connected adjacent panels. There is thusprovided a close spaced relation of the emission surfaces. This is aswould be effected on elongation or expansion of the structure from aflat folded relation with the panels in face engagement.

The disclosed interfolded structure in addition to its rigidity has amaterially enhanced filament efliciency resulting from the permissibleuse of fine gauge fabric and a greater degree of compactness resultingin decreased heat radiation. It further has maximum emission areasthereby to obtain high thermionic cathode efiiciency by a close spacingbetween the panel emission surfaces which spaces are of a formation tomake the structure regenerative.

An illustrative embodiment of the improved emission electrode structureis shown in Fig. 4 wherein the emitter is employed as a cathode of athermionic gas filled diode rectifying tube.

In the structural arrangement as shown, the tube which may be of thetype employing ionizable mercury vapor comprises the customary base 6containing insulatingly supported terminal pins 1 connected by wires 8to the tungsten lead supports 9. The supports have spaced upper endsupon which the cathode is supported and connected by having its endscomposed of the two strip layers of wire mesh material, welded thereto.Supported above the cathode in suitably spaced relation is the anode IE1of inverted cup formation. Surrounding the cathode and its mounting isthe usual filament shield l l secured to a shielding disc support l2mounted upon a central supporting rod l3 supported within the lowerpress l 4. The upper end portion l5 of the shield is of reducedcylindrical form extended within and in spaced relation to the anode toprovide the usual upper vent for the ionizing chamber 16 within theshield. The anode is connected to an output lead I! connected to theupper terminal l8 supported upon the reduced end IQ of the usual glassenvelope 20 containing the mercury vapor charge. Insulatingly supportedupon the leads and positioned in spaced relation below the shield is alower heat shield 2| upon which the usual getters 22 containingvaporizable magnesium are supported as shown. In this disclosedembodiment of rectifying tube the cathode of the improved structuralformation as described is mounted as shown to be positioned edgewiserelative to the anode or target surface. The cathode may be mountedother than as shown to suit specific conditions.

While the invention is described with respect ,4 to a desirableembodiment of the features thereof it will be understood that variedmodifications may be made therein without departing from the scope ofthe invention as defined in the appended claims. As illustrative thereofwhile the method of making refers to the initial folding of the strip orribbon lengths to provide a reverse fold strip with subsequentinterfolding of the strips it will be understood that in manufacture thestrips may be folded and interwoven as a, progressive operationsimultaneously to produce the assembled and finished product. Also whiletwo strips are employed in the preferred structure as shown, three ormore strips may be interfolded in similar manner with resulting changein form of the panels. In the instance of the interfolding of the threestrips a hexagonal composite panel formation will result as is readilyunderstood.

What is claimed is:

1. An electrode consisting of metallic strips folded on substantiallytransverse lines with progressive reverse bends and having the stripsinterfolded in angularly disposed relation.

2. An electrode as claimed in claim 1 wherein the strips are of metallicmesh material,

3. An electrode as claimed in claim 1 wherein the strips are of metallicfabric coated with thermionically active oxides.

4. An electrode consisting h of metallic strips folded on substantiallytransverse lines with successive reverse bends and having the stripsinterfolded in angularly disposed relation with the formed panelsextended into angular spacing relation.

5. An electrode consisting of multiple strips of wire mesh materialreversely folded on substantially transverse lines with successivereverse bends to be of zig-zag form and having the strips interfolded inangularly disposed relation with the formed panels disposed in acuteangular relation.

6. An electrode consisting of metallic strips reversely folded onsubstantially transverse lines with qually spaced and successive reversebends and having the strips interfolded in angularly disposed positionwith the formed panels disposed in acute angular spacing relation.

'7. A cathode for electron discharge devices consisting of metallicstrips folded on transverse lines with successive reverse turns andhaving the strips interfolded in angularly disposed relation to presentstrip material on edge in planes disposed at substantially ninetydegrees angularity.

8. A cathode for electron discharge devices consisting of strips ofmetallic mesh material folded on transverse lines with successivereverse turns and having the strips interfolded in angularly disposedrelation to present strip material on edge in planes disposed atsubstantially ninety degrees angularity and having its resulting panelin acute angular and spaced relation.

9. A cathode for electron discharge devices consisting of multiplestrips of wire mesh material folded on substantially transverse lineswith successive reverse bends and interfolded in angularly disposedrelation of the strips to present strip material on edge in planesdisposed at substantially ninety degrees angularity and with expansionof the structure to position the resulting panels in angular and spacedrelation and said strips being coated with a thermionically activeoxide,

10. A cathode for electron discharge devices consisting of multiplemetallic strips reversely folded on substantially transverse lines andinterfolded angularly disposed relative to one another with the bends ofeach strip embracing the free panel edges of the companion stripalternately at opposite sides thereof and having the resulting panelformations in angular relation.

11. A cathode for electron discharge devices consisting of two metallicstrips reversely folded on equally spaced transverse lines andinterfolded to be angularly disposed relative to one another with thebends of each strip embracing the free panel edges of the companionstrip alternately at opposite sides thereof and having the resultingpanel formations in acute angular relation.

12. A cathode for electron discharge devices consisting of two metallicmesh strips folded on transverse lines with successive reverse bends andinterfolded in angular position relative to one another With the bendsof each strip embracing the free panel edges of the companion stripalternately at opposite sides thereof and having the resulting panelformations extended into acute angular spacing relation and said stripsbeing coated with thermionically active material.

13. The method of making electrodes for elec* tron discharge devicesconsisting in reversely folding strips of metallic material ontransverse lines and interfolding the strips angularly disposed relativeto one another with the bends of each strip embracing the free paneledges of the other strip alternately at opposite sides thereof.

14. The method of making electrodes for electron discharge devicesconsisting in reversely folding strips of metallic material on equallyspaced transverse lines and interfolding the strips angularly disposedrelative to one another with the bends of each strip embracing the freepanel edges of the other strip alternately at opposite sides thereof.

15. The method of making electrodes for electron discharge devicesconsisting in reversely folding strips of metallic material of uniformwidth on equally spaced transverse lines and interfolding the stripsangularly disposed relative to one another with the bends of each stripembracing the free panel edges of the other strip alternately atopposite sides thereof and with the formed panels in angular spacedrelation.

16. An electron discharge device comprising an enclosing envelope,electrodes supported within the envelope in spaced relation including ananode and an electron emitting ribbon cathode formed of multiple stripseach of which is folded on transverse lines successively in reverseddirection and interfolded in angularly disposed relation of the stripsWith the formed panels in angular and spaced relation providing acellular structure, said cathode being supported with an edge of therectangular structure directed toward the anode, input leads to thecathode and an output lead connected to the anode.

17. An electron discharge device comprising an enclosing envelope,electrodes supported within the envelope in spaced relation including ananode and an electron emitting ribbon cathode formed of multiple wiremesh strips each of which is folded on transverse lines successively inreversed direction and interfolded in angularly disposed relation of thestrips with the formed panels in acute angular and spaced relationproviding a cellular structure, said cathode being supported with anedge of the rectangular structure directed toward the anode, input leadsto the cathode and an output lead connected to the anode.

18. An electron discharge device comprising an enclosing envelope,electrodes supported within the envelope in spaced relation including ananode and an electron emitting ribbon cathode formed of multiple stripsof wire mesh each of which is folded on equally spaced transverse linessuccessively in reversed direction and interfolded in angularly disposedrelation of the strips with the formed panels in acute angular andspaced relation providing a cellular structure, said cathode beingsupported with an edge of the rectangular structure directed toward theanode, input leads to the respective ends of the cathode, an output leadconnected to the anode and said strips being coated with athermionically active oxide. 1

WILLIAM WIDMAIER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 21,222,021 Etzrodt Nov. 19, 19401,913,432 Denzler June 13, 1933

